Grips Employing Deflection (Capstan Grips)

A load reduction curve is used for this specimen grip. The force in the specimen is reduces over the course of the load reduction curve. The required gripping forces can be reduced in the pneumatic control unit. Maximum test load ranges from 500 N to 20 kN.

Grips with 90° Deflection

For specimens prone to shrinkage, the closing force is uniformly maintained by constant pneumatic pressure.

The contact force on the specimen is reproducible.

Automatic centering of specimen via guide groove.

Function description

Function Description

A reduction curve is used for this specimen grip. The force in the specimen is reduces over the course of the load reduction curve. The specimen is held by the pneumatic end clamp. The required gripping forces can be reduced in the pneumatic control unit by the load reduction curve.

The specimen grip can also be used without the load reduction curve. To do so, it is mounted at a 90° (see illustration).

Frictional forces between rollers and specimen eliminates slippage of the specimen.

Function description

The double capstan grips can be used to grip threads and thread-like tensile
specimens.

With this deflection principle a force slope occurs in two stages. The specimen break takes place in the gage length without causing slippage of the specimen on the lower roller or jaw breaks.

The specimen is looped over the load cell roller. The specimen is then deflected to a lower roller and guided to a third height-adjustable roller.

After the deflection of the double thread, a pre-load weight (not included in scope of delivery) is attached. During this stage all three rollers are movable. The extensions, which are created when the pre-load weight is attached, are balanced. The three lengths are aligned to the material being tested.

The double thread is clamped into the wedge grip. This is also height adjustable.

After the specimen grip is closed the deflection rollers are locked. Frictional forces between the rollers and the specimen prevents slippage of the specimen. The roller diameter is dimensioned in such a way that the occurring friction does not influence the test results.

A specimen grip with constant gripping force is used to clamp the double thread because the specimen to be tested can frequently slip out from between the gripping areas.

Specimen grip for steel strip cord

The symmetrical weight distribution allows the center of gravity of the grips in the tensile axis. No transverse forces are transmitted to the load cell via the specimen grips.

A guide groove is integrated into the load reduction roller and basic unit for thread feeding, allowing fast and convenient specimen feeding and automatic and precise positioning in the tensile axis.

Force reduction curve employing 270° deflection reduces the tensile force on the end-clamping position. Thus the required closing force can be reduced at end clamping for specimens that are sensitive to clamping. The closing force is progressively loaded at end clamping, thereby securely holding the specimen and preventing jaw breaks during the test.

The load reduction radius is reduced seamlessly via the involute form of the load reduction roller.

The ends are clamped pneumatically, ensuring that the gripping force remains constant even with diminishing specimen diameter.